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Power Science

New Rechargeable Battery Uses Water 179

Posted by samzenpus
from the I-want-my-water-engine dept.
fergus07 writes "Scientists at Stanford have developed a battery that uses nanotechnology to create electricity from the difference in salt content between fresh water and sea water. The researchers hope to use the technology to create power plants where fresh-water rivers flow into the ocean. The new 'mixing entropy' battery alternately immerses its electrodes in river water and sea water to produce the electrical power."
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New Rechargeable Battery Uses Water

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  • by Osgeld (1900440)

    so does the one in my lawnmower, I thought lead acid batteries have been around a while, maybe I just live in the future

  • by Skal Tura (595728) on Thursday May 05, 2011 @09:28AM (#36035002) Homepage
    It's gizmag ... Prepare to be annoyed with ads
  • by retroworks (652802) on Thursday May 05, 2011 @09:33AM (#36035072) Homepage Journal
    Like, recharging your flashlight at the urinal.
  • by naich (781425) on Thursday May 05, 2011 @09:43AM (#36035186) Homepage

    We could use the generated electricity to power desalinisation plants.

    • by ShanghaiBill (739463) on Thursday May 05, 2011 @09:57AM (#36035336)

      We could use the generated electricity to power desalinisation plants.

      I think you are trying to be funny, but this actually makes sense, and there are proposals to do exactly this. Here is how it works:

      • Step 1: Concentrate brine in large evaporation ponds
      • Step 2: Generate electricity from the osmotic difference between this brine and normal seawater
      • Step 3: Use the electricity to split seawater into fresh water and brine
      • Step 4: Recycle the brine back into the evaporation ponds
      • Step 5: Profit!

      The reason this works is that you are effectively collecting the solar energy that shines on the evaporation ponds.

      • by trout007 (975317) on Thursday May 05, 2011 @10:16AM (#36035584)

        Not that this would be ecologically feasible but what if you dug a tunnel from the pacific ocean to death valley (-300 feet). Then you could get some power out of the potential water drop. Then as the water floods the valley it's so hot it would evaporate and you could keep letting the water in. The evaporated water would rain on the next mountain down wind and create arable land.

        • Probably be more feasible for Mediterranean -> Dead Sea, but then you'd have to tunnel through numerous archaeological sites to do it.

        • by spikenerd (642677)
          Why tunnel? Wouldn't a big siphon be easier to build?
          • by Isaac-1 (233099)

            Siphons have a maximum theoretical height limit relating to the minimum pressure inside at the peak. Simply put when the pressure gets low enough to boil water at ambient temperature then the siphon no longer works.

             

        • Re: (Score:3, Funny)

          by Anonymous Coward

          San Andreas Fault thinks your tunneling is cute.

      • by MoonBuggy (611105)

        Interesting, but what's the advantage of this over condensing the vapour from the pools directly?

        • Interesting, but what's the advantage of this over condensing the vapour from the pools directly?

          It is orders of magnitude less expensive. If you want to condense the vapor, you first need to collect the vapor. Evaporation ponds typically cover thousands of hectares. Building an enclosure to collect the vapor over such an area would cost megabucks or even gigabucks. Once you collect the vapor you need to compress and cool it to turn it into liquid water. This is also very expensive.

          If simply evaporating seawater was a cost effective way to produce fresh water, the world would have not water shorta

      • by pr0nbot (313417)

        Isn't Step 1 already splitting seawater into fresh water and brine?

      • by Solandri (704621)

        * Step 1: Concentrate brine in large evaporation ponds
        * Step 2: Generate electricity from the osmotic difference between this brine and normal seawater
        * Step 3: Use the electricity to split seawater into fresh water and brine
        * Step 4: Recycle the brine back into the evaporation ponds
        * Step 5: Profit!

        The reason this works is that you are effectively collecting the solar energy that shines on the evaporation ponds.

        No it doesn't work. Well, it would work, but it'd be less effective

        • I think its easier to have acres and acres of solar collectors than it is to build a structure over the top of that.

      • by idji (984038)
        You perhaps forgot the energy costs of dredging the salt out of your pond when it gets too shallow.
    • by Xacid (560407)

      I see what you did there...

    • by wjousts (1529427)
      Perpetual motion FTW!
    • That would give us enough salt to last forever!!
    • From the article: "In fact, the fresh water doesn't have to come from a river. Cui says that storm runoff, gray water, or even treated sewage water could potentially be used. As an added benefit, the mixing entropy process can be reversed to produce drinking water by removing salt from ocean water."
    • by SEWilco (27983)
      Because, of course, if your fresh/salt water plant is next to a fresh water river, there isn't any source of fresh water nearby, so you have to desalinate the salt water.
  • by dr.Flake (601029) on Thursday May 05, 2011 @09:45AM (#36035212)

    I know the plans to put one of these into service are almost finalized in The Netherlands, spanning the "afsluitdijk"
    http://wikimobi.nl/wiki/index.php?title=Zoet/zout_watergrens [wikimobi.nl]

    But i think the Norwegians beat us all to it:

    http://www.statkraft.com/energy-sources/osmotic-power/ [statkraft.com]

    • by arielCo (995647)

      Depends on how wide your definition of "this" is. Let's quote TFA for convenience:

      Making electricity from the difference in salinity (the amount of salt) in fresh water and sea water is not a new concept. We've previously covered salinity power technology [gizmag.com], and Norway's Statkraft [gizmag.com] has built a working prototype power plant. But the Stanford team, led by associate professor of materials science and engineering Yi Cui, believes their method is more efficient, and can be built more cheaply.

    • by wjousts (1529427) on Thursday May 05, 2011 @10:09AM (#36035510)

      ...spanning the "afsluitdijk".

      Cat just jump on your keyboard?

    • by rawler (1005089)

      TFA explicitly mentions the Statkraft project. However, there seems to be a significant difference between the two; where statkraft is using the salinity to create pressure and power a conventional turbine generator, this article is about creating current directly, which should theoretically improve efficency a lot.

      According to TFA a, 50cubic meter/second flow of fresh water could yield up to 100MW.

  • Bass Akwards! (Score:4, Insightful)

    by CatsupBoy (825578) on Thursday May 05, 2011 @09:51AM (#36035280)

    After the battery is discharged, the salt water is drained and fresh water is added to begin the cycle again.

    This is awesome, we can use up all our fresh water and would have an unlimited supply of salt water!

    • You do know that there is an amazingly simple way to separate the salt from the water, right? It is called evaporation.
      • Re:Bass Akwards! (Score:4, Insightful)

        by CatsupBoy (825578) on Thursday May 05, 2011 @10:11AM (#36035530)

        You do know that there is an amazingly simple way to separate the salt from the water, right? It is called evaporation.

        The concepts of desalination are certainly quite simple, its the economics that are complicated.

        • You do know that there is an amazingly simple way to separate the salt from the water, right? It is called evaporation.

          The concepts of desalination are certainly quite simple, its the economics that are complicated.

          He means natural evaporation. Oceans are under the Sun all the time. You can't "use up" fresh water by intercepting water that's about to fall on the ocean and making it into salt water. That is happening all the time anyway, those rivers are constantly dumping fresh water into the ocean. Luckily, water evaporates off the oceans and comes back down as fresh water as rain, filling up those rivers and continuing the cycle.

    • by JSBiff (87824)

      This certainly wouldn't be appropriate everywhere. But, consider the Mississipi River Delta. It's dumping massive amounts of fresh water into salt water anyhow.

      It hardly seems like diverting a small percentage of the fresh water being dumped into the ocean by nature, extracting power from it as it gets salty, then dumping the brackish water from the power plant into the ocean, in any reasonable way reduces the fresh water supply, does it?

      Or, do you propose that we completely dam up the Mississippi so we don

    • by timeOday (582209)
      Good lord, they headed off that complaint right in the summary, and it still wasn't enough.
  • This sounds like something that would just finish off the migrating salmon population if implemented.
  • Im getting a sort of deja vu feeling because i'd swear i've heard of this, or a similar, process before.
    • It looks like a potato battery (that we used to make little clock kits back in the 80s) or any galvanic battery dating back 100+ years, but with a tweak to get more out of it, implemented on a larger scale, and slapped with a "New and Improved, now with NANOTECHNOLOGY" sticker.

    • I think what's new isn't the basic science, but the R&D to try to scale this up to commercial size power plants?

      Still, I can't help but think that at some point, this is going to create contention somewhere between some peoples' need for fresh water, and other peoples' need for electricity.

      I guess the idea is that places like the Mississippi Delta where a lot of fresh water is just dumping into the ocean (and being "wasted") *anyhow*, it wouldn't hurt to put such a power plant.

  • The Stanford team has calculated that with 50 cubic meters (more than 13,000 gallons) of fresh water per second, a power plant based on this technology could produce up to 100 megawatts of power.

    I can't find any facts detailing the flow of water through various hydroelectric dam turbines to compare to this, but 100MW from 50m^3/s seems very efficient.

  • by scharkalvin (72228) on Thursday May 05, 2011 @09:58AM (#36035350) Homepage

    In Florida most drinking water is obtained from wells. Deep wells tend to be brackish and require desalination of the water to be usable. It would seem then that a combination use of waste water and deep well water would work. Also the battery sounds like it acts as a desalination device during discharge so it might serve the purpose of both desalination and power generation.

    • by Nidi62 (1525137)

      In Florida most drinking water is obtained from wells. Deep wells tend to be brackish and require desalination of the water to be usable.

      So that explains why Florida has some of the worst-tasting drinking water in the entire country.

  • From the article:

    "The Stanford scientists are currently working on modifications to get the battery ready for commercial production. For example, the silver electrode is very expensive, and they hope to develop a cheaper alternative."

    I'm really at a loss on this. How expensive can a silver electrode be, if you're producing enough power to charge for it? Silver while pricey (currently ~ $39.00/oz) It's just a tad more expensive than Lithium (currently ~ $31.50/oz) and if this thing really worked. they'd pay

  • Wouldn't this "leach" material from the electrodes into the water?

    Normally, batteries work by leaching material from one electrode into the water, while precipitating ions on the other. By draining the battery, you actually "consume" one of the electrodes. Recharging work if the process can be reversed.

    However, if the electrolyte is changed between charging and decharging, effectively the manganese dioxide or silver ions dissolved are now gone, which has two effects:

    • pollution
    • electrode whose ions are gone
  • by DriedClexler (814907) on Thursday May 05, 2011 @10:40AM (#36035888)

    In learning about thermodynamics I had learned that, where there's a gradient, you can extract energy, be it a gradient of temperature, electrical field ... or even chemical concentration. But it's one thing to know it's theoretically possible, and another thing to actually pull it off in a way that extracts meaningful energy. Good work, scientists and engineers.

    • by Belial6 (794905)
      You comment is funny for me. Just a bit ago I posted a comment about how every single person who brings up thermodynamics on Slashdot doesn't know what it means. And then here I find, possibly the first, comment about thermodynamics on Slashdot with a an actual clue.

      Well done.
      • Glad to hear it! But I didn't know I was saying something all that insightful or demonstrative of thermodynamics understanding.

        It is kind of counterintuitive that you'd be able to extract energy just because there's a difference in concentration between two bodies, but it makes more sense once you've read about the Gibbs paradox (esp. Jaynes's handling) and how you can power a mechanical device by using membranes that differ in their permeability to the different constituents of the mixture.

        But man, if eve

  • Will this magic power plant at the side of the ocean require new electrodes/new electrodes every few hours because of pitting and erosion, just like normal batteries?
  • by tacokill (531275) on Thursday May 05, 2011 @11:05AM (#36036206)
    So, 13,000 gallons per second of fresh water flow and we can get around 100MW. Let's go on a math exercise, shall we?

    The average combined cycle plant is (at a minimum) around 400MW. Not including co-gens, etc. Just normal power plants sitting out in the middle of nowhere. Fukishima is around 4900MW. Fukishima isn't really fair because it is, by any measure, a large nuke plant. But, 400-1200MW is not an unreasonable range for "typical" power plants in the US, regardless of the technology used (coal, nuke, combined cycle, direct fire, etc)

    At 400MW, you are talking 52,000 gallons PER SECOND of water flow. That, by any measure, is a shitload of flow. At 1200MW, we are talking 156,000 gallons per second.

    For comparison, I just looked up the flow rate of the Mississippi river at the high water dam near Lake Itasca. Going thru the Upper St Anthony's falls lock and dam, the flow rate is around 90,000 gal/sec [nps.gov].

    So for ONE reasonably sized power plant, you would need fresh water flow that is the equivalent of the Mississippi River.

    As I said, it's a scale problem.
    • by steelfood (895457)

      In comparison, the hoover dam generates 2.08 GW, and niagara falls 2.4 GW. And in the most extreme case, the three gorges dam does 18.2 GW.

      It may work on small scales, but it cannot compete with hydroelectric on a large scale.

    • by gurudyne (126096)

      Uh, you are looking through the telescope the wrong way. That flow you quoted is at the UPPER end. From the same site you linked to, the flow is 50 times greater at the Delta, where you find the OTHER side of the cell, salt water.

    • by holmstar (1388267)
      For a large-ish 2000MW plant, it would need 260000 gallons per second of fresh water. At the MOUTH on the Mississippi (where it meets the ocean), that would make up about 5.8% of the over all flow of the river. Not as big of a deal as you are suggesting

      If you diverted a quarter of the flow (probably possible, if not practical), you could supply a plant that provides over 8000MW. It would certainly be a big facility, but that's also a lot of electricity.

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